Method of drying wet thread



June 11, 1940. H B, UN Er 2,204,500

I HETH 0D O F DRYING WEI THREAD I Original Filed Oct. 26, 1936 3 Sheets-Sheet 2 [mam/.1 vzemn/ if U Patented June 11, 1940 UNITED STATES PMATENTOFFICE METHOD OF DRYING WET THREAD Original application October 26,1936, Serial No. 107,667. Divided and this application May 12,

1938, Serial No. 207,530

3 Claims. 01. 34-24) This application, which is a division of copendingapplication Serial No. 107,667. relates to the drying of continuouslengths of materials, such as thread or the like, under circumstances inwhich provision is made for the shrinkage of such materials. Moreparticularly, the invention relates to the continuous drying of suchmaterial while stored in a plurality of generally helical turns on awinding reel permitting controlled shrinkage of the material being driedon the reel. While the invention may be employed to advantage in thedrying of any kind of thread or the like which shrinks while beingdried, it may be employed to particular advantage in the drying ofartificial silk thread produced by any' of the known wet-spinningprocesses, such, for example, as the viscose, nitro-cellulose andcuprammonium processes.

While the invention is applicable to the drying of a wide variety ofmaterials, generically referred to as thread or the like,for convenienceit will be described hereinafter as applied to the drying of viscoseartificial silk thread.

It is desirable that viscose artificial silk thread shall have along itslength uniform physical and physico-chemical characteristics, this beingparticularly true in respect of what may be called its residual capacityto shrink. The term "residual capacity to shrink may be defined as theamount, in proportion to its original dry length, a dry thread will, ifunrestrained in any manner, shrink upon being rewet and redried.Residual capacity to shrink is imparted to a thread which is preventedfrom completely shrinking as it is dried, the amount-of shrinkage whichthe thread is permitted to experience before being preventcd fromfurther shrinking being determinative of its residual capacity toshrink. Uniformity of residual capacity to shrink is, however, extremelydifficult to attain.

Uniformity of these physical and physicochemical characteristics isparticularly desirable in thread employed in the weaving of fabrics. Insuch fabrics, the cloth is initially woven to a width substantiallyequal to or slightly greater than the desired width of the finishedfabric. In the finishing operations, the woven fabric, after beingwashed, dyed, etc., is dried in tentering frames which hold the fabricto the desired finished width. If the thread of which the fabric isformed has a high residual capacity to shrink, tearing of the fabricmayresult during the drying operation, due to stresses set up in the fabricas it shrinks while being thus held in the tens tering frames. For thisreason, it is desirable that the thread forming the fabric have a lowresidual capacity to shrink, particularly since the looms used in theweaving industry, being of fixed widths, may not be adjusted tocompensate for excessive shrinkage stresses.

Non-uniformity in such characteristics causes imperfections in thefinished cloth, which imperfections are especially noticeable in dyedfabrics. Moreover, the manner of drying the thread, particularly in thecase of viscose artificial silk thread, determines to a large extent theuniformity and amount of residual capacity to shrink imparted to thethread, as well as the uniformity of other physical and physlco-chemicalcharacteristics of the thread. For this reason, it is diflicult tomanufacture wholly satisfactory woven fabrics from artificial silkthread produced by a wet-spinning process in which the thread is driedon the spool on which it is collected. Such thread does not possess asatisfactory degree of uniformity, particularly in respect of thedesired low residual capacity to shrink. This arises from the fact thatthe thread does not shrink evenly when dried on the spool.

As a result, thread which has been dried while wound on a spool has aresidual capacity to shrink which varies widely at different pointsalong its length. For instance, portions of the thread which are wounddirectly on the spool, being prevented thereby from shrinking on drying,havea high residual capacity to shrink, as do also portions on the outersurface of the cake which, due to their rapid drying, are prevented fromshrinking by the inner layers of thread. Other portions of the threadwhich are permitted to shrink more or less freely, such as the portionsof thread in the inner layers of the cake, have a relatively lowresidual capacity to shrink. If such thread is woven into a fabric whichis dried on a tentering frame, the fabric will not shrink uniformly, dueto such varying residual capacities to shrink, which adversely affectthe uniformity with which the fabric may be dyed. The portions of threadof high residual capacity to shrink are subjected to higher tensionsthan other portions as the cloth is dried, thus giving rise to brightstreaks known to the fabric trade as shiners.

Heretofore, most of the wet-spun artificial silk thread manufactured forthe weaving industry has therefore been produced by a process in whichthe yarn is unwound while wet from the package in which it is collected,such package being eitherla pot-spun cake or a cake of thread wound on aspool, after which it is reeled into skein form. In the latter form, thethread, after being subjected to various processing steps, is

dried while hanging loosely, thus permitting substantially freeshrinkage of the thread. Since the weight of the thread as it hangs fromthe skein rods while drying tends to stretch certain portions of thethread and since all portions of the thread do not dry at the same rate,the thread inside of the skein winding dries more slowly than the outerportions of the thread, thus introducing variations in the physical andphysico-chemical properties of the thread. It is therefore virtuallyimpossible to obtain skeindried thread which is of as high a degree ofuniformity as might be desired. Furthermore, such methods entail a largeamount of handling, with consequent disadvantages of excessive breakageof thread, high labor costs, large investment in machinery, plant space,etc., all of which factors tend to make weaving thread comparativelyexpensive.

By the present invention, it is possible to produce thread which is ofuniform physical and physico-chemical characteristics along its entirelength, having in particular a uniform, predetermined residual capacityto shrink which may be as low as desired. The thread, because of thecontrol over the shrinkage made possible by the present invention, is ofa higher quality than the best that it has heretofore been possible tomanufacture on a commercial scale. It is particularly well suited toemployment in the weaving of fabric. The thread is dried whiletemporarily stored on a winding reel in a plurality of spaced, advancinggenerally helical turns, the reel being adapted to permit eithersubstantially complete shrinkage of the thread or unrestrained shrinkageof the thread to a point at which a desired residual capacity to shrinkis imparted to the thread. Therefore, highly uniform artificial silkthread well suited for weaving may be produced at a much lower cost thanhas been heretofore possible.

Because of the improved means of drying the threadprovided by thepresent invention, artificial silk thread may, as part of a continuousprocess, be unwound from the package in which it was collected, dried ona winding reel embodying the principles of this invention, and

thereafter collected in suitable form. Such operations may be performed,for instance, by means of the apparatus shown, described and claimed inprior copending applications Serial Nos. 41,425 and 41,426, both filedSeptember 20, 1935, in which one or more winding reels are employed forprocessing thread supplied thereto directly from the spinning package.If desired, the thread may be dried according to this invention onapparatus of the general type shown, claimed and described in priorcopending application Serial No. 7,114, filed February 18, 1935. For thepurposes of convenience and illustration, but in no sense of limitation,the invention will be de scribed in connection with the drying ofviscose artificial silk thread on a reel forming'part of a. machine forthe continuous manufacture of artificial silk thread, of the generaltype disclosed in the above-mentioned applicationserial No. 7,114.

In the drawings, Figure 1 is a side elevation of a portion of themachine of the general type shown in said last-mentioned application.Figure 2 is a front elevation of the same machine. Figure 3 is a sideelevation on an enlarged scale of a winding reel on which the thread maybe dried according to this invention, parts being aaoasoo broken awaymore clearly to show the construction thereofu Figure 4 is an endelevation of the reel from line 3-3 of Figure 3. Figure 5 is a graphshowing the amount of shrinkage of viscose artificial silk thread forvarious moisture contents. Figures 6 and 7 show diagrammatic profilecontours of reels on a larger scale than Figures 3 and 4. Figure 8 showsdiagrammatically a preferred profile contour of a reel embodying theinvention, revealing the relation of the thread to the reel duringoperation thereof.

In the drawings, like reference characters refer to like partsthroughout.

In the apparatus illustrated in Figures 1 and 2, the thread I from asuitable source, such as a coagulating bath in which it has been formed,is passed in sequence to and over each of a series of suitable windingreels on each of which it is subjected to one or more desired processingtreatments, three such reels, bearing reference numerals 2, 3 and 4,being shown in these figures. On reels on which processing liquid isapplied to the thread, of which reel 2 is typical, the processingliquid, which in this case may be wash water, is applied by a suitabledistributor 5 supplied by pipe 6 from a supply manifold I which mayextend longitudinally of the machine and serve like reels in ahorizontal series. The liquid is collected in a suitable trough 8 whichmay be disposed beneath the reel and likewise extend longitudinally ofthe machine. .On reel 3 no processing liquid need be applied, the threadbeing simply stored on said reel to provide a period for allowing excessliquid to drip from the thread. The thread is then passed to reel 4 onwhich it is dried according to the present invention. It is collected bysuitable means, such as cap-twister 9.

Winding reels 2, 3 and 4 may, as illustrated, be of cantilever form,having one end free and unobstructed as shown, in which case the reelsmay be disposed in a stepped arrangement as illustrated. Such anarrangement is advantageous in that it provides ready access to thereels for threading up, inspection, replacement, repair, etc. Each ofthe reels may be driven as illustrated through gears III and I I from adrive shaft l2 driven from a main drive shaft I3 which extendslongitudinally of the machine and drives each of the drive shafts I2 fora vertical series of reels. Cap-twister 9 may be actuated in theconventional manner whereby a belt I4, driven by suitable means, mayrapidly rotate the bobbinsupporting whirl I 5 while it is beingvertically reciprocated by chain I6 which may be actuated by anysuitable means.

The reel illustrated inFigures 3 and 4 as embodying the inventioncorresponds to drying reel 4 of the apparatus of Figures 1 and 2. Thisreel is of a type similar to the reel shown, described, and claimed in acopending application Serial No. 652,089, filed January 16', 1933. Fromthese figures it can be seen that each reel comprises two rigidgenerally cylindrical members I! and I8. Member II, which may be termedthe concentric member, is mounted concentrically upon and for rotationwith drive shaft l9 and has its periphery comprised of a plurality ofbar members 2|. Member I8, which may be termed the eccentric member, maybe rotatably mounted with its axis slightly offset from and askew tothat of member I1 and has its periphery comprised of a plurality of barmembers 22 equal in number to the bar members 2| and alternatelydisposed there-.

with.

iii?

Concentric member l1 may be formed as shown with the bar'members 2|formed on the periphery of a cylindrical body 23; inwhich' case greatrigidity is obtained. While member I! may be mounted on the drive shaftIS in various manners. in that shown the generally cylindrical body 23thereof is provided with'slots 26 at the rear end, in which slots aredisposed theends of pin 24 mounted in drive shaft l9 against which pin24 generally cylindrical body 23 is held by a cap-- nut threaded intothe end of drive shaft i9. Concentric member I! is thus caused to rotatewith shaft I! by means of pin 24.

Eccentric member I8 is formed of a rigid cagelike member 21 mountedconcentrically upon an annular supporting member 28 as by bolts 29.Rigid cage-like member 21 is formed of the aforesaid bar members 22which are provided at their supported ends with an external supportingrib 3| by means of which the cage-like member 21 is mounted on annularsupporting member 28. Annular supporting member 28 is rotatablysupported in the desired ofiset and askew position with respect to theaxis of concentric member I! by being rotatably mounted on frame member32, the shaft 19 being journalled in or otherwise supported in thedesired relationship to frame member 32. A bushing 33 may, if desired,be provided in annular supporting member 28 to act as a bearing.

Rotation of reel drive shaft l9 causes ocncentrio member l'i fixedthereto to rotate, whereupon contact of bar members 2| of concentricmember I! with bar members 22 of eccentric member l8 causes saideccentric member to rotate at the same angular speed. During suchrotation, the offset rotation of the generally cylindrical members l1and It causes the thread to transfer from the bar members of onegenerally cylindrical member to the bar members of the other generallycylindrical member. At the same time, the askew relationship of thegenerally cylindrical members causes the thread to advance in aplurality of spaced generally helical turns lengthwise of the reel.

The other reels 2 and 3 of the illustrated apparatus may be of the samegeneral type and operate in the same general manner.

As the thread is continuously stored on the drying reel 4 (Figures 1 and2), it is dried by suitable means. In the apparatus illustrated, thedrying is accomplished by means of heated 'air supplied from a supplymanifold 35 through the shaft IQ of the reel 4 which may be made hollowfor this purpose. The heated air passes through the holes 36 in shaft I9(Figure 4) to a chamber 31 in the interior of the cylindrical body 23 ofconcentric member ll. It reaches the thread stored on the reel throughthe holes 38 which may extend toward the spaces between the bars 2| ofconcentric member H. In order to intensify the drying action, providebetter control over the drying operation, and conserve the heated air, asuitable housing 39 may be provided, the same being supplied, ifdesired, with a door 4| by means of which access may be obtained to thereel 4. The air may pass through return duct to an exhaust manifold 43whence it may pass to suitable reconditioning and reheating means, notshown, after which it may be recirculated back throughsupply manifold35.

If the reel is made of metal having good heat 2 conductivity, asaluminum, drying of the thread of heat through the reel members to thethread. as well as by convection of the air.

According to the present invention, provision is made for allowingsubstantially unrestrained shrinkage of the thread I as it is driedwhile being progressed lengthwise of the drying reel 4 in a plurality ofspaced generally helical turns. In the illustrated embodiment of theinvention, as shown in Figures 3 and 4, this is accomplished by makingthe thread-bearing periphery of the reel of such form that substantiallyunrestrained strinkage of the thread occurs thereon for at least aportion of the length of the periphery of the reel. Particularly, theperiphery of the reel is so designed as in part to permit the thread todry out of actual contact with the reel.

To aid in better understanding the function of the reel in permittingsubstantially unrestrained shrinkage of the thread, a typical freeshrinkage curve has been reproduced in Figure 5. The curve of Figurerepresents the percentages of free shrinkage of the thread from thelength in the wet condition for various percentages of moisture in thethread. The moisture content, plotted as the abscissa, is the proportionthat the weight of the moisture in the thread bears to the weight of thebone dry thread at any given time, while the percentage of shrinkage,plotted as the ordinate, is the proportion that the reduction in lengthof the thread due to shrinkage bears to the original wet length of thethread for a given moisture content. As can be seen from this curve, asthe moisture content of the thread is reduced by drying, as from 300% toapproximately 150%, very little shrinkage of the thread occurs. However, at a moisture content of approximately 150%, noted as point B onthe curve, pronounced shrinkage of the thread begins, which shrinkageincreases as .themoisture content of the thread is reduced. When themoisture content of the thread is reduced to zero, the thread for whichthe curve of Figure 5 was determined shrinks somewhat more than 6% ofits original length.

The occurrence of but slight shrinkage of the thread while its moisturecontent is being reduced from 300% to 150% may be due to the fact thatsubstantially all of the moisture removed from the thread during thisdrying phase may be surface moisture, while the high percentage ofshrinkage which occurs while the moisture content of the thread isreduced from 150% is probably due to a change in the structure of thethread during the removal of internal moisture from the thread. It hasbeen found that moisture is rapidly removed from the thread until itsmoisture content is reduced to the point of pronounced shrinkage,whereas the remaining moisture is removed from the thread more slowly.This is probably due to the fact that the surface moisture is rapidlyremoved by evaporation, while the remaining moisture in the thread isremoved more slowly by diffusion.

As drying of the thread occurs when it is stored on the reel in aplurality of spaced generally helical turns, the diameter of thegenerally helical turns of thread will tend to decrease due to shrinkageof the thread. For a given set of drying conditions, a given set ofoperating conditions of the reel, including a given spacing of theshrinkage is unrestrained, define a surface having diameters decreasingfrom the initial diameter of the generally helical turns in which thewet thread was wound to a smaller diameter determined by the amount ofshrinkage of the thread, the curvature of the portion of the surface ofrevolution between the two portions of different diameters beingdetermined by the shrinkage characteristics of the thread. It has beenfound possible to determine a peripheral form of a winding reel theprofile contour of which corresponds to the theoretical profile contourwhich would be defined by the thread as it shrinks under the abovecircumstances. For a given set of conditions, this contour of the reelwill permit unrestrained shrinkage of the thread. A typical theoreticalprofile contour of a reel for free shrinkage of thread which is driedunder certain drying conditions on a winding reel of the general typeand construction shown in Figures 3 and 4 is diagrammatically shown inFigure 6. It will be noted that, from the point a at which the threadstarts on the reel to the point I), the reel is substantiallycylindrical; from point 2) to point the diameter of the reel diminishes,the profile contour between point b and point 0 being a curve from thelarger diameter of portion a-b of the reel to a smaller diameter; whilefrom point 0, at which shrinkage of the thread cases, to the point d, atwhich the thread leaves the reel, the reel is substantially cylindrical.

When the thread is stored in a plurality of spaced generally helicalturns and advanced from point a to point D while being dried, it losesexcess moisture, being in the condition corresponding to the portion ofthe curve of Figure 5 to the right of point B thereof. By the time itreaches point D on the reel, it has had its moisture content reduced tothe point corresponding to point B of Figure 5, at which pronounced thethread being meanwhile in the condition place, as'is evidenced by'thegenerally cylindrical portion extending from c to the end of the reel.

While, as indicated, on a reel having this theoretical contoursubstantially unrestrained shrinkage of the thread is possible for agiven set of operating conditions and for a given kind of thread, anymarked variation in the drying conditions, the speed of the reel, thekind of thread being dried, etc., will necessitate a change in thiscontour. It has been found, however, that, by modifying the contour ofthe reel from the theoretical contour in a manner provided by thepresent invention, satisfactory results may be obtained, even overwidely varying operating conditions and with threads of widely varyingsizes and physical characteristics. To more clearly Since it must beremoved by dif-.

explain the form and operation of a reel having a preferred peripheralcontour, in Figure 'l the theoretical profile contour of Figure 6 hasbeen superposed in broken lines on the preferred profile contour, shownin full lines, of a winding reel embodying the invention, which reel forthe purposes of correlation is of the same general construction andwhich is designed to operate over a range of conditions which includethe operating conditions for the reel embodying the theoretical profilecontour of Figure 6.-

The preferred contom of a reel embodying the invention is substantiallysimilar to the theoretical contour, as shown in Figure '7. As before,the reel may comprise two generally cylindrical portions A-B and CDhaving between them an intermediate portion BC so formed that it variessomewhat from the portion 17-0 of the ideal contour, the diameters ofportion 3-0 of the preferred reel being less than the correspondingdiameters of a reel having the ideal contour, as shown in Figure 7. Inother words, at least a portion of the periphery of the reel over whichpronounced shrinkage of the thread takes place decreases in diameter ata greater rate, as the turns of thread are advanced along said portion,than the diameter of each turn of thread tends to decrease due toshrinkage of the thread. As a result, substantially unrestrainedshrinkage of the thread is allowed to take place over such a portion ofthe reel.

The diameters of the portion CD of the reel may be such as to determinethe amount of residual capacity to shrink imparted to the thread; thatis, the generally cylindrical portion CD may be of such diameter thatthe thread leaves the tapered portion BD and starts on the portion CD,as at point E, before it is completely shrunk. In such case, drying ofthe thread is completed on the generally cylindrical portion CD and adefinite, uniform, controlled residual capacity to shrink is imparted tothe thread. If desired, the diameters of portion CD may be such as toallow the thread to shrink completely, in which case the thread may haveno residual capacity to shrink. As shown in Figure '7, however, thediameter of portion CD of a reel of the preferred contour is slightlylarger than the corresponding portion of a reel of the theoreticalcontour shown, thus providing a certain small amount of residualcapacity to shrink in the thread. However, if desired, a reel having atheoretical ,contour may also be similarly made larger at thecorresponding portion to provide a desired amount of residual capacityto shrink in thread which may be dried on a reel having such contour. Byvarying the diameter of generally cylindrical portion CD withinreasonable limits, it is possible to vary the residual capacity toshrink imparted to the thread. Thus, by increasing the diameter ofportion CD, the residual capacity to shrink imparted to the thread maybe increased; while by decreasing such diameters, the residual capacityto shrink imparted to the thread may be decreased.

Furthermore, if desired, the generally cylindrical portion C'--D of areel of the preferred contour may, as illustrated, be somewhat longerthan is necessary to dry the thread to the desired moisture content,since such longer portion may provide an additional setting period forthe thread to reach equilibrium drying conditions before it leaves thereel. As previously indicated, the thread may not be dried to a bone-drycondition, but to a condition in which the thread has a moisture contentof around 10% of the bonedry weight of the thread, corresponding to theordinary regain moisture content of thread produced by ordinary methods.This moisture is advantageous if, as in the illustrated embodiment, thethread is twisted after leaving the drying reel, since a moisturecontent of this amount aids in the twisting operation.

The position of the thread on the reel while being dried is shown toadvantage in the diagrammatic view of Figure 8, which shows in profilethe preferred contour of the reel and the cross-section of the threadsthereon. figure, the first helical winding of the wet thread starting onthe reel comes into contact with the reel at A. The thread may be verywet, having a moisture content which may be in the neighborhood of 300%.As the thread is advanced axially of the reel it is dried, as byconvection of the heated air supplied from the interior of the reel andby the conduction of the heat through metallic bars of the reel. Themoisture content 01' the thread is reduced as the thread is advancedalongportions A--B of the reel at such a rate that, as the threadreaches the vicinity of point B, it is in the condition corresponding topoint B on the moisture content-shrinkage curve of Figure 5, at whichpoint pronounced shrinkage of the thread begins. The portion A-B of thereel may be substantially cylindrical, since the amount of shrinkage ofthe thread as its moisture content is reduced to the point to whichpronounced shrinkage of the thread commences is so small as to be almostnegligible. The contour of the portion A-B of the reel may, if desired,be of such shape as to conform to even such slight amount of shrinkageof the thread.

While the thread has been quite firmly supported on portion A--B of thereel, it is loosely supported when it is advanced over the-portion ofthe diminishing diameters BC of the reel, due to the previouslymentioned fact that the reductions of the diameters of the reel, as thethread advances along this portion, are greater than the reductions indiameters of the corresponding turns of thread occurring from shrinkageof the thread. This is illustrated by the fact that, during operation ofthe reel the thread turns on portion B-C of the reel actually leave thereel during rotation thereof, as shown in Figure 8, only occasionallytouching the reel. The action of the reel as the thread turns advancealong theportion BD thereof is not so much that of supporting the threadturns, but that of guiding and advancing the thread turns. The thread isthus allowed substantially unrestrained shrinkage until it comes intocontact with the portion C-D of the reel, on which portion, if desired,the shrinkage of the thread may be halted and the drying of the threadallowed to proceed to completion. Thus, by suitably de- 4 signing thereel, there may be imparted to the thread a definite uniform residualcapacity to shrink which may, within reason, he of any desiredmagnitude.

The invention contemplates the employment of reel contours of variouskinds in the portion of the periphery over which unrestrained shrinkageof the thread is permitted to occur, but in general a straight linecontour such as that of portion BC of the reel shown and described ispreferred.

The conditions affecting the operation of the reel, such as the kind ofthread being dried, the

temperature and humidity of the heated air,

In this speed of rotation of the reel,etc., may be varied withreasonable limits without an appreciable variation in the physicalproperties of the thread or of the residual capacity to shrink thereof.This arises from the fact that the thread is loosely supported whileshrinkage thereof occurs, and, while such variations vary the rate ofdrying of the thread, they merely change the position longitudinally ofportion C-D of the point E at which the thread leaving the taperedportion BC of the reel comes into contact with the generally cylindricalportion C-D thereof. Thus, if the operating conditions are so variedthat the thread dries somewhat more rapidly, and consequently shrinksmore rapidly, the point E at which the thread contacts the generallycylindrical portion C-D moves nearer point C, while, if the thread isdriedmore slowly, the point E moves away from point C.

The amount the thread shrinks and the residual capacity to shrinkimparted to the thread are thus not aifected by such variations indrying conditions, since the thread is in each case permittedunrestrained shrinkage until it reaches portion C--D. This advantage isnot obtained on a reel having a tapered portion which decreases indiameter more gradually than the thread turns tend to decrease due toshrinkage. In such case, the thread is under an appreciable amount oftension as it passes over the tapered portion of the reel, since anyvariation in the drying conditions causes the thread to complete itsdrying at difierent portions on the tapered portion of the reel, thusvarying the amount of shrinkage occurring in the thread as well as theresidual capacity to shrink imparted to the thread.

Because of the fact that reels of the type embodying the preferred formof the invention may operate under varying conditions withoutappreciable variations in the final physical properties of the thread,it is therefore possible to dry a plurality of threads, as on apparatusof the type illustrated in Figures 1 and 2, without appreciablevariations from thread to thread in the residual capacities to shrink ofthe thread or in other physical and chemical properties which may beaffected by variations in drying conditions. This is particularlyadvantageous, since in the operation of machines in which large numbersof threads are dried, it is not commercially practicable to maintainexactly uniform and identical drying conditions for all of the threads;yet by means of reels embodying the present invention it is possible tohave all threads produced on such apparatus of substantially identicalphysical properties.

As an illustrative example of the operation of a reel having a contourof the type shown in Figure 8, it has been found in actual practice thatdesirable results are obtained in drying 150 denier 40 filament viscoseartificial silk thread on an aluminum drying, reel of the typeillustrated in Figures 3 and 4. In such reel the diameters of the reelmembers at the portions A-B thereof may be 4.950"; the diameters of theportions of the reel members at portions C-D thereof,

4.700"; the distance from the point A at which the thread starts on thereel to point B, as"; and the distance from point B to-C, 1 The reel ispreferably rotated at approximately 165 R. P. M., the thread beingsupplied from a preceding reel rotating at the same speed and havingreel' members of 5 diameters at their discharge ends. Due to theconstruction of the reel, the thread is advanced in a plurality ofgenerally helical turns which are spaced approximately 1 6" apart. It isdried by heated air supplied at 185 F. at a static pressure of about 6"of water. The finished thread has along its entire length a very uniformlow residual capacity to shrink very closely approximating 0.6%, allother physical and chemical characteristics of the thread being also ofa high degree of uniformity.

It has been found, further, that the amount of tension in the wet threadat the commencement of the drying operation determines to an appreciableextent the amount of residual capacity to shrink imparted to the threadwhen it is dried on the reels of the present invention. Thus if thethread is under relatively great tension at the beginning of the dryingoperation, theresidual capacity to shrink imparted to the thread will behigher than if the thread is under relatively little tension at thecommencement of the drying operation. For this reason, it is desirablethat, at the commencement of the drying operation, the thread be underas little tension as practicable for satisfactory operation of the reel.

Where the thread is dried on an individual drying reel, as in theillustrated embodiment of the invention, this may be accomplished byproviding a peripheral speed of that portion of the drying reel on whichthe thread first starts on the reel; 1. e., portion AB of the reel,which is less by a suitable amount than the linear speed at which thethread is supplied to the reel from the source of thread. Thus, in theillustrated apparatus in which the thread passes from a preceding reelto the drying reel, the peripheral speed. of portion AB of the dryingreel may be less than the peripheral speed of the discharge end of thepreceding reel. This may be accomplished, for instance, by making theportion A-B of the drying reel and the discharge end of the precedingreel of the same diameters and rotating both reels at different angularspeeds, or by making the diameter of portion AB of the drying reel lessthan that of the discharge end of the preceding reel and driving bothreels at the same speed, or by a combination of these methods. As a re--suit, any tension in the thread will be released, the thread, if it isat all stretched, being allowed to contract as it starts on the dryingreel. As an example of the efiect of the initial tension of the threadon the residual capacity to shrink imparted to the thread the followingis illustrative:

Viscose artificial silk thread is dried according to the above-outlinedmethod on an aluminum reel, of the type above described. The reel is 5"long and has reel members 5" in diameter at the end at which the threadis started on the reel. The difference in the diameters of portions A-Band CD of the reel is 4 the reel being rotated at R. P. M. The thread isdried by heated air supplied from the interior oi the reel at F. Thediameter of portion AB of the reel is the same as that of the dischargeend of the preceding reel and both reels are driven at the same speed.Consequently, no attempt is made to release any tension existing in thethread. The residual capacity to shrink of the thread so dried is in theneighborhood of Thread of the same kind is dried on a reel of the samegeneral dimensions as the reel of the preceding example, the onlydifference being that the diameter of portion AB of the reel is 1% lessthan the diameter of the discharge end of the reel immediately precedingit. In this case, as in the preceding case, there is a difference of l/2% between the diameters of portions AB 6 and C-D of the reel. Both thereel in question and the reel immediately preceding it are rotated at165 R. P. M., the thread being dried by heated air at 185 F. suppliedfrom the interior of the drying reel. The residual capacity to shrink isin the neighborhood of .5%.

Thus it is apparent that the amount of tension existing in the thread atthe commencement of the drying operation appreciably aiiects theresidual capacity to shrink imparted to the thread.

It is apparent that the type of reel in connection with which thisinvention has been described is purely illustrative and that theinvention may be applied to reels operating on various other principles.It may be applied to reels on which the thread is dried by other meansthan heated air, as in the examples herein given. Furthermore, reelsembodying the invention may be employed for other uses and in otherarrangements than those herein illustrated without in any way 2..

invention. 3:

What is claimed is:

1. The method of drying wet thread under conditions such that shrinkageof the thread may proceed to a considerable extent substantially withoutrestraint comprising the steps of con- 44 tinuously winding the wetthread to form a first series of firmly supported generally helicalturns in which some tension is present, eliminating tension from thethread by advancing it in the form of a second series of looselysupported gen- 4 erally helical turns, and reintroducing tension intothe thread by further advancing it in the form of a third series offirmly supported generally helical turns, the thread while in suchhelical form being heated to a temperature high enough to removemoisture from the thread.

2. The method of drying wet thread comprising the steps of continuouslywinding the wet thread in a plurality of generally helical turns upon athread-advancing device heated to a temperature high enough to removemoisture from the thread, the thread being wound upon said device undera degree of tension such that the turns are supported firmly; advancingthe thread lengthwise of said device in the form of a travel- (a inghelix characterized by loosely supported generally helical turns whichare substantially free from tension, meanwhile removing moisture fromthe thread to an extent such that a substantial amount ofunrestrainedshrinkage takes place; i. and, after halting shrinkage ofthe thread by further advancing it lengthwise of said device in aplurality of generally helical turns in which the thread is again underenough tension so that the turns are supported firmly, continuously un-7 winding the dried thread from said threadadvancing device.

3. The method of drying wet thread comprising the steps of continuouslywinding the wet thread in a plurality of generally helical turns 7 upona thread-advancing device heated to a temperature high enough to removemoisture from the thread, the thread being wound upon said device undera degree of tension such that the turns are supported firmly; advancingthe thread lengthwise of said device in the form'of a traveling helixcharacterized by loosely supported generally helical turns which aresubstantially free from tension, meanwhile removing moisture from thethread to an extent such that a substantial amount of unrestrainedshrinkage takes place;

and, after completion of the drying operation, continuously unwindingthe dried thread from 5 said thread-advancing device.

HAYDEN B. KLINE. LAVERN J. JORDAN.

